The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section.
Plastic films with thermal adhesive backing are used for decorating a wide variety of materials and products. While these films are sometimes referred to as heat transfer vinyl, modern heat transfer films are usually manufactured from urethane, polyester, or polypropylene to avoid the toxicity of vinyl chloride when exposed to heat.
Cut thermal adhesive films are composed of at least two layers, the plastic substrate, and a thermal adhesive coating. The substrate often contains a colorant or additional decorative additive. The films are usually affixed to a backing paper or plastic substrate. Films of this type may be cut with a plotter/cutter machine so that regions of the film cut film may describe lettering or a decorative shape or image. Often the films are cut in a manner that leaves the backing film or paper intact. The type of cutting is called a ‘kiss cut’.
After cutting, the portions of the film that do not include the lettering or shape to be transferred must be removed. The non-transferred portion of the film is called the ‘negative area’. Removing the negative areas of the film for all but the simplest designs is performed by heat press operators as a manual process. The manual removal of negative areas of heat transfer films is called ‘weeding’. After weeding, the positive areas of the film are transferred using a heat press to the surface of the material or product to be decorated.
The labor costs for weeding constrains the complexity of designs that may be used for decorating objects with heat transfer films. While there are other processes such as pad printing, screen printing, and direct inkjet printing that may easily handle complex designs, heat transfer films may be formulated to adhere to and decorate a much wider variety of materials and combination of materials found in products than other decorative printing processes. Heat transfer films may also be manufactured with metal films or flakes or be embossed to form other optically active surfaces.
Given the versatility of heat transfer films, it is useful to devise a system and method for the automated removal, or weeding, of the negative design areas prior to heat transfer that is integrated into the application of the cut thermal transfer film.